1. Technical Field
This disclosure is directed to integrated circuits, and more particularly, to providing access to internal circuitry through a debug access port.
2. Description of the Related Art
Boundary scan testing was originally developed to test connections between integrated circuits (IC's) and printed circuit boards (PCB's) in the absence of other ways to probe them. Boundary scan is based on the Joint Test Action Group (JTAG) specification, which is also known at the Institute of Electrical and Electronic Engineers (IEEE) Standard 1149.1. In particular, the IEEE 1149.1 standard provided a mechanism for providing access to pins of an IC to determine the presence of proper connections.
Although the IEEE 1149.1 standard was originally developed for boundary scan, its uses have expanded to other areas. For example, JTAG ports are now used to obtain access to an IC for debugging during the development phase. For example, a JTAG controller may be used to access portions of an IC while conducting tests of system software in a new design.